Foundational Investigation on the Characterization of Porosity and Fiber Orientation Using XCT in Large-Scale Extrusion Additive Manufacturing

Tagscherer, Nevine; Schromm, Thomas; Drechsler, Klaus

doi:10.3390/ma15062290

Cited by 8 publications

(7 citation statements)

References 34 publications

(56 reference statements)

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“…In the LS-MEX process, the addition of carbon fibres not only improves the mechanical properties but also the processability [27]. The reduction in residual thermal stresses due to the use of carbon fibres enables the production of large components, as the fibres absorb the stresses generated during the process.…”

Section: Materials Polyamide 6 Reinforced With 40 Wt% Carbon Fibresmentioning

confidence: 99%

Crystallisation Dynamics in Large-Scale Extrusion Additive Manufacturing: An Analysis with and without Temperature Modification

Leubecher,

Brier,

Vitale

et al. 2024

Materials

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Large-Scale Material Extrusion (LS-MEX) is increasingly being used in small-scale production and prototyping due to its ability to create components in new temporal and spatial dimensions. However, the use of this manufacturing process poses microscopic and macroscopic challenges not encountered in previous small-scale production systems. These challenges arise primarily from the prolonged retention of heat in the material, which leads to insufficient strength in the extruded strands at the macrostructural level. As a result, the component can collapse, a phenomenon known as ‘slumping’. Thermal energy also influences microstructural changes, such as crystallisation kinetics, which affect properties such as the strength and stiffness of the final product. The duration and dynamics of thermal energy are influenced by manufacturing parameters and the possible use of additional peripheral equipment, which affects component quality. In this study, the influence of thermal energy on structural processes through simulations of polyamide 6 with 40% carbon fibres (PA6 wt.%40 CF) is investigated. The results show that by adjusting the process parameters and using modification units, the thermal profile of the material can be accurately controlled, which allows the microstructural processes to be precisely controlled. This leads to the targeted modification of the macroscopic material properties. The focus of this work is on the combination of numerical simulations of the LS-MEX process with semi-empirical methods for the analysis of crystallisation processes. The application of the Nakamura model, which is used throughout similar investigations, allows a detailed description and prediction of the crystallisation kinetics during the manufacturing process. The study shows that the absolute degree of crystallisation can be determined with simplified assumptions using a combination of thermal simulations and semi-empirical approaches. It was found that the absolute degree of crystallisation increases from the outer interface of the strand to the print bed across the cross-section. This can be attributed to the specific thermal boundary conditions and the resulting temperature profiles at different points.

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Section: Materials Polyamide 6 Reinforced With 40 Wt% Carbon Fibresmentioning

confidence: 99%

Crystallisation Dynamics in Large-Scale Extrusion Additive Manufacturing: An Analysis with and without Temperature Modification

Leubecher,

Brier,

Vitale

et al. 2024

Materials

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“…Different studies have conducted investigations on porosity effects on the mechanical performance of AM-fabricated CFRP composites [5][6][7][8][9][10][11][12]. However, there are still limited investigations on the quantitative comparison of fabrication temperature-related porosity effects.…”

Section: Current Understanding Of Deposition Temperature-related Poro...mentioning

confidence: 99%

Fabrication Temperature-Related Porosity Effects on the Mechanical Properties of Additively Manufactured CFRP Composites

Adeniran¹,

Osa-uwagboe²,

Cong³

et al. 2022

Preprint

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The use of additive manufacturing in fabricating composite components has been gaining traction in the past decade. However, some issues with mechanical perfor-mance still need to be resolved. The issue of material porosity remains a pertinent one that needs more understanding to be able to determine viable solutions. Different re-searchers have examined the subject of porosity issues in AM-fabricated CFRP compo-sites. However, more research to quantitatively determine the effects of fabrication temperatures at the micro-scale is still needed. This study employed micro CT scan analysis to quantitatively compare the effects of fabrication temperatures at 230°C, 250°C, 270°C, and 290°C for CF-PA and CF-ABS composites. This followed an SEM evaluation which was used to determine the effects of the temperatures on interlayer and intralayer porosity generation. The porosity volume was related to the mechanical properties results in which it was determined how deposition temperatures affect the porosity volumes. It was also determined that semicrystalline composites are generally more affected by fabrication temperatures than amorphous composites, with the rela-tionship between porosity and mechanical properties also established. The overall po-rosity volume from the interlayer and intralayer voids was also determined, with the interlayer voids found to play a more determinant role in influencing the mechanical properties.

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“…Layer height (LH) is another critical factor affecting the formation of voids, with conflicting reports presented in the literature. In some samples, increasing LH has been shown to reduce the number and size of the pores at the layer interfaces [17]. In other samples, increasing LH increased the number of pores and size of voids [18,19].…”

Section: Introductionmentioning

confidence: 99%

“…They demonstrated that higher substrate temperatures can reduce void volume. Conversely, lower processing temperatures can increase the number and size of voids [17]. Layer height (LH) is another critical factor affecting the formation of voids, with conflicting reports presented in the literature.…”

Section: Introductionmentioning

confidence: 99%

Size Effects in Polycarbonate and TPU 3D-Printed via Fused Filament Fabrication

Chadha,

Olaivar,

Mahrous

et al. 2024

Preprint

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This paper investigates the influence of sample size and layer height on the elastic modulus of samples 3D printed by fused filament fabrication (FFF). Cubic samples of different sizes from either a stiff thermoplastic polymer (polycarbonate (PC)) or a soft polymer (thermoplastic polyurethane (TPU)) were printed at three different layer heights: 0.1 mm, 0.2 mm, and 0.4 mm. The samples were imaged using micro-computed tomography to visualize porosity and tested under compression. The results indicate that the elastic modulus of TPU varied with sample size, demonstrating size effects due to high porosity. In contrast, PC samples had a low void volume fraction and did not demonstrate statistically significant size effects on the elastic modulus. The variations in elastic modulus due to layer height were statistically significant for both materials. The highest elastic modulus was observed at 0.2 mm layer height for both materials across different sample sizes, which can be attributed to low void volume fractions. The study develops process-structure-property relations for PC and TPU samples manufactured by FFF. It provides new insights into the design guidelines for FFF based on the size effects. The results indicate that variations in mechanical properties due to size effects must be considered during the design stage for TPU to accurately predict the material’s behavior. Additionally, the locations of the printed parts that are subjected to higher loads should be printed closer to the heated print bed due to the lower void volume fraction observed in the section of the samples printed adjacent to the heated print bed.

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Foundational Investigation on the Characterization of Porosity and Fiber Orientation Using XCT in Large-Scale Extrusion Additive Manufacturing

Cited by 8 publications

References 34 publications

Crystallisation Dynamics in Large-Scale Extrusion Additive Manufacturing: An Analysis with and without Temperature Modification

Crystallisation Dynamics in Large-Scale Extrusion Additive Manufacturing: An Analysis with and without Temperature Modification

Fabrication Temperature-Related Porosity Effects on the Mechanical Properties of Additively Manufactured CFRP Composites

Size Effects in Polycarbonate and TPU 3D-Printed via Fused Filament Fabrication

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